DE102007059084B4 - Process for the production of biogas - Google Patents

Abstract

Method for producing biogas (B) from a substrate (S1) having a first ammonium nitrogen concentration of more than 5.0 kg NH ₄ -N / m ³ , in particular poultry droppings, with the following steps:
Reducing the first ammonium nitrogen concentration to a predetermined value by heating the substrate (S1),
Producing a mixture of the substrate (S1) having the predetermined value of the first ammonium nitrogen concentration and a fermentation substrate containing a further substrate (S2),
Determining a second ammonium nitrogen concentration of the fermentation substrate and
Setting the second ammonium nitrogen concentration in the fermentation substrate in such a way that a minimum value of 3.0 kg NH ₄ -N / m ³ is not fallen below and a maximum value of 5.5 kg NH ₄ -N / m ³ is not exceeded, wherein the fermentation substrate
(I) for lowering the second ammonium nitrogen concentration of a fermented digestion withdrawn and purified by a reverse osmosis process water (P) and
(ii) to increase the second ammonium nitrogen concentration to the fermentation substrate (S1)
is added.

Description

The The invention relates to a method for producing biogas from substrates with a high first ammonium nitrogen concentration, in particular Poultry.

The DE 10 2005 047 719 A1 discloses a method for producing biogas from biomass with high solids and nitrogen contents. In this case, a digestate formed during fermentation is separated into two partial streams. A first partial stream is recirculated to mash new biomass. In a stripping process, ammonia / ammonium nitrogen is withdrawn from a second substream and then separated into a solid and a liquid phase. The liquid phase is also recirculated to mash new biomass.

At the Stripping process, the ammonium nitrogen content is reduced by 70% to 90%. As a result contains the recirculated liquid Phase of the second partial flow up to 30% ammonium nitrogen. To one too high an ammonium content in the fermentation substrate and to avoid a consequent nitrogen inhibition, can at the known method only a relatively small proportion of a high ammonia nitrogen concentration containing poultry faeces fermentation substrate added become. Usually amounts to the proportion of chicken droppings on the fermentation substrate not more than 25% by weight.

The DE 103 53 728 A1 relates to a process for the production of biogas. Here, a partially fermented substrate is removed from the reactor and separated into a solid and a liquid phase. The liquid phase is freed by a stripping process essentially of ammonium and ammonia. The liquid phase is then mixed with the solid phase in a mixing vessel. 40 to 80% by volume of the solid / liquid mixture are returned to the reactor.

From the EP 1 762 607 A1 is a regulatory procedure for biogas plants known. The ammonia value of a fermentation substrate is maintained at a predetermined desired value by adding appropriate control substrates. The return of a processed fermentation residue in the biogas reactor is not provided.

The DE 10 2004 030 482 A1 relates to a process for the treatment of waste water from the processing and treatment of organic waste, in particular manure, with a biogas fermenter. Fermenter residues are removed from the fermenter and subjected to a solid-liquid separation. Part of the solid phase is returned to the fermenter. The liquid phase is subjected to ultrafiltration and reverse osmosis. The purified liquid phase is partially recycled to the fermenter. The aim of the method is the production of a einleitfähigen, especially agriculturally usable, water.

From the DE 10 2004 003 458 A1 is a method for residual waste processing known. The denitrification of a process water takes place by means of a stripping device.

Currently the prices rise for Renewable raw materials due to rising demand. Poultry excrement is because of its high nitrogen content, however, usually not to be disposed of without further ado and is given free of charge as a result.

task The present invention is to provide a simple and inexpensive feasible Process for the recovery of biogas from fermentation substrates with a high Content of ammonium nitrogen, in particular poultry excrement, indicate.

These The object is solved by the features of claim 1. Expedient refinements result arising from the features of the claims 2 to 18.

• (i) zum Erniedrigen der zweiten Ammonium-Stickstoffkonzentration einem vergorenen Gärrest entzogenes und mittels eines Umkehrosmoseverfahrens gereinigtes Prozesswasser und
• (ii) zum Erhöhen der zweiten Ammonium-Stickstoffkonzentration dem Gärsubstrat erstes Substrat

zugesetzt wird.According to the invention, a method is provided for producing biogas from a substrate having a first ammonium nitrogen concentration of more than 5.0 kg NH ₄ -N / m ³ , in particular poultry droppings, with the following steps:
Reducing the first ammonium nitrogen concentration to a predetermined value by heating the substrate,
Producing a fermentation substrate containing a mixture of the substrate having the predetermined value of the first ammonium nitrogen concentration and a further substrate,
Determining a second ammonium nitrogen concentration of the fermentation substrate and
Setting the second ammonium nitrogen concentration in the fermentation substrate in such a way that a minimum value of 3.0 kg NH ₄ -N / m ³ is not fallen below and a maximum value of 5.5 kg NH ₄ -N / m ³ is not exceeded, wherein the fermentation substrate

• (I) for lowering the second ammonium nitrogen concentration of a fermented digestion withdrawn and purified by a reverse osmosis process and process water
• (ii) for increasing the second ammonium nitrogen concentration to the fermentation substrate first substrate

is added.

With the proposed method, it is possible to ver fermentation substrates with a high proportion of substrates with a high first ammonium nitrogen concentration, in particular poultry faeces ferment. In contrast to the prior art, it is thus possible to convert fermentation substrates with a proportion of more than 30% by weight of poultry droppings into biogas. According to the invention, this is achieved in particular by a suitable adjustment of the second ammonium nitrogen concentration in the fermentation substrate. In this case, for particularly efficient processing of the substrate, the second ammonium nitrogen concentration is preferably set close to the maximum value, for example in a range of more than 4.0 kg NH ₄ -N / m ³ to 5.5 kg NH ₄ -N / m ³ . A particularly preferred range of the second ammonium nitrogen concentration ranges from a minimum value of 4.5 kg NH ₄ -N / m ³ to a maximum value of 5.5 kg NH ₄ -N / m ³ .

To the Adjusting the aforementioned ranges of the second ammonium nitrogen concentration it may either be required, the second ammonium nitrogen concentration to humiliate or increase. According to the invention is for Lower the second ammonium nitrogen concentration to a fermented one digestate withdrawn and purified by a reverse osmosis process Process water added. Such process water has an extremely low Ammonium concentration on. It's so clean it is can be disposed of by discharge into receiving waters or rivers. By to Lowering the second ammonium nitrogen concentration process water On the one hand, the consumption of valuable fresh water can be used avoided and on the other hand, an entry of ammonium in the fermentation substrate be avoided. As a result, the fermentation substrate, a particularly high Proportion of substrate or poultry droppings be added.

To set the aforementioned range of the second ammonium nitrogen concentration, it may also be necessary to increase it. For this purpose substrate is added to the fermentation substrate. Since the substrate generally has a first ammonium nitrogen concentration of more than 5.0 kg NH ₄ -N / m ³ , in particular more than 10.0 kg NH ₄ -N / m ³ , can thus the second ammonium nitrogen concentration increases and at the same time an efficient disposal of the substrate can be achieved.

To an advantageous embodiment is for determining the second Ammonium nitrogen concentration is the ammonium content or the ammonia content in the fermentation substrate measured. In that regard, can According to the prior art known measuring devices are used. advantageously, the second ammonium nitrogen concentration is determined by means of known Measuring device continuously measured and monitored.

In similar The first ammonium nitrogen concentration in the substrate can also be obtained be determined. Also for this purpose, the ammonium content or the ammonia content in the substrate can be measured. It is located the substrate in a separate reservoir.

To proviso The invention provides that the first ammonium nitrogen concentration by heating the substrate prior to addition to the fermentation substrate is reduced to a predetermined value. The default Value in dependence the second ammonium nitrogen concentration and the amount of fermentation substrate and the amount of the substrate. For heating the substrate can advantageously by exhaust gas generated by burning biogas be used. Biogas, for example, can be used to drive a generator to be burned. - By the proposed heating of the substrate to a temperature, for example in the range of 50 ° C up to 100 ° C Ammonium contained in it is removed in the form of ammonia. In order to can the first ammonium nitrogen concentration in a simple way adapted to the respective requirements. The respective ones Requirements are influenced by the amount of fermentation substrate, the second ammonium nitrogen concentration, an amount of another Substrate and the nature of the other substrate.

Usually a third ammonium nitrogen concentration of the further substrate is smaller as the first ammonium nitrogen concentration. As a result, can also by the nature of the other substrate and its proportion in the fermentation substrate the second ammonium nitrogen concentration are lowered. The Further substrate can essentially be made from renewable vegetable raw materials be formed. Since the inventive method in particular efficient disposal of highly nitrogen-containing substrates, in particular poultry feces, is directed, the second ammonium nitrogen concentration in the fermentation substrate lowered by the addition of process water. Furthermore, a humiliation achieved by heating the substrate. Another humiliation can be achieved by mixing the substrate with the other substrate become.

To A further embodiment of the invention provides that for the preparation of the fermentation residue from the fermentation substrate settling sediment by means of a coiler agitator in fermented fermentation substrate is suspended. Such a way suspended digestate can be removed by a pump from a fermentation reactor. That allows one particularly simple process control.

According to a further embodiment feature, solids contained in the digestate in a further process step are separated by means of microfiltration, preferably ultrafiltration. The pellets thus produced form a valuable rieselfähi dry fertilizer.

To a further advantageous embodiment is in the Reverse osmosis process by a multi-stage process in which expediently a first reverse osmosis and subsequently a second reverse osmosis is carried out.

advantageously, may be part of a remaining after separating the solids from the digestate residual liquid withdrawn and as a liquid fertilizer or used for its production. The residual fluid is subsequently advantageously further by means of the reverse osmosis process cleaned. It falls on the one hand purified process water, which for adjusting the second ammonium nitrogen concentration is used. Further falls in the process another residual liquid, which in turn as liquid fertilizer or can be used for its production.

If according to the aforementioned Design of the method residual liquid and / or other residual liquid is withdrawn, is expediently an approximately the volume of the withdrawn residual liquid and / or further residual liquid corresponding volume of liquid added to the fermentation substrate. It can act as a liquid used in the substrate or in the further substrate water become. If this water is not sufficient, any remaining Differenzvo lumen by the addition of additional liquid, preferably fresh water, Residual water or sewage, be balanced. For example, as Residual water in fruit juice production sloping liquids used to compensate for the difference volume.

following is an embodiment of the invention with reference to the drawing explained in more detail.

The single drawing shows schematically a procedure. Poultry manure with a first ammonium nitrogen concentration of more than 5.0 kg NH ₄ -N / m ^{3 is} used as substrate S1. As a further substrate S2, biogenic residues, for example corn or the like, are used. Their second ammonium nitrogen concentration is less than the first ammonium nitrogen concentration. It is usually less than 3.0 kg NH ₄ -N / m ³ . The first substrate S1 and the further substrate S2 are placed in a mixer 1 given. There, a mixture is prepared which contains at least 30% by weight of first substrate S1 and at most 70% by weight of second substrate S2.

Substrate S1 is added to the mixer prior to addition 1 heated to lower the first ammonium nitrogen concentration. In this case, heat can be used to heat the substrate S1, which is decoupled, for example, from a biogas-operated cogeneration plant. As a result of the heat treatment liberated ammonia is used to neutralize a neutralizer 2 fed. This may be an acid scrubber, for example a sulfuric acid scrubber.

For the preparation of a fermentation substrate, process water P and, if necessary, additional fresh water F are added to the mixture. After setting a suitable consistency, the fermentation substrate thus prepared is placed in a reactor 3 transferred. In this case, an ammonium nitrogen concentration in the reactor 3 , preferably continuously, determined and regulated so that a minimum concentration of 3.0 kg NH ₄ -N / m ^{3 is} not undershot and a maximum concentration of 6.5 kg NH ₄ -N / m ^{3 is} not exceeded. To maintain the aforementioned concentration range, fermentation substrate is supplied to a suitable ammonium nitrogen concentration. The H ₂ S concentration is in the reactor 3 suitably adjusted so that it does not exceed a value of 100 mg / l.

To suspend solids is in the reactor 3 a reel mixer 4 intended. The reference symbol B denotes biogas, which is formed during the fermentation of the fermentation substrate and from the reactor 3 is dissipated to generate energy.

Once the fermentation substrate is substantially fermented, it is by means of the coiler agitator 4 suspended and in a downstream liquid / solid phase separation device 5 , z. As a decanter, pumped. There, the substantially fermented fermentation substrate is separated into a solid phase and a liquid phase.

The liquid phase is purified by ultrafiltration UF and then subjected to a, preferably two-stage, reverse osmosis UO. After performing a first reverse osmosis stage, a liquid phase is generated which can be decoupled from the process and used as liquid fertilizer. After performing a second reverse osmosis stage process water P accumulates, which the mixer 1 for the preparation of the fermentation substrate is supplied. Excess process water P can be withdrawn from the process if necessary.

The from the liquid / solid phase separation device 5 withdrawn solids can be dried and subsequently pelleted. They can either be used as fertilizer, composted or even burned.

1

mixer

2

neutralizer

3

reactor

4

reel agitator

5

Liquid / solid phase separator

B

biogas

F

fresh water

P

process water

S1

substratum

S2

additional substratum

UF

ultrafiltration

UO

reverse osmosis

Claims (18)

Process for the production of biogas (B) from a substrate (S1) having a first ammonium nitrogen concentration of more than 5.0 kg NH ₄ -N / m ³ , in particular poultry excrement, comprising the following steps: reducing the first ammonium nitrogen concentration to one predetermined value by heating the substrate (S1), preparing a mixture of the predetermined value of the first ammonium nitrogen concentration having substrate (S1) and a further substrate (S2) containing fermentation substrate, determining a second ammonium nitrogen concentration of the fermentation substrate and adjusting the second ammonium nitrogen concentration in the fermentation substrate such that a minimum value of 3.0 kg NH ₄ -N / m ³ does not fall below and a maximum value of 5.5 kg NH ₄ -N / m ^{3 is} not exceeded, the fermentation substrate (i) for lowering the second ammonium nitrogen concentration, a process water withdrawn from a fermented digestate and purified by a reverse osmosis process (P) and (ii) adding the substrate (S1) to the fermentation substrate to increase the second ammonium nitrogen concentration. The method of claim 1, wherein for determining the second ammonium nitrogen concentration of the ammonium content or the ammonia content in the fermentation substrate is measured. Method according to one of the preceding claims, wherein determines the first ammonium nitrogen concentration in the substrate (S1) becomes. Method according to one of the preceding claims, wherein to determine the first ammonium nitrogen concentration of the ammonium content or the ammonia content in the substrate (S1) is measured. Method according to one of the preceding claims, wherein the default value depending on from the second ammonium nitrogen concentration as well as the amount of the fermentation substrate and the amount of the substrate (S1) is determined. Method according to one of the preceding claims, wherein for heating the substrate (S1) by burning biogas (B) produced exhaust gas is used. Method according to one of the preceding claims, wherein a third ammonium nitrogen concentration of the further substrate (S2) is less than the first ammonium nitrogen concentration. Method according to one of the preceding claims, wherein the further substrate (S2) consists essentially of renewable vegetable Raw materials is formed. Method according to one of the preceding claims, wherein for the preparation of the fermentation residue from the fermentation substrate abset Zendes sediment by means of a reel agitator ( 4 ) is suspended in the fermented fermentation substrate. Method according to one of the preceding claims, wherein the fermentation residue by means of a pump from a fermentation reactor ( 3 ) is discharged. Method according to one of the preceding claims, wherein in the digestate contained solids by microfiltration, preferably by means Ultrafiltration (UF), to be separated. The method of claim 11, wherein the separated Solids are composted or pelleted. Method according to one of the preceding claims, wherein in the reverse osmosis process, a first reverse osmosis and subsequently a second reverse osmosis is performed. Method according to one of claims 11 to 13, wherein a part one remaining after separation of the solids from the digestate residual liquid withdrawn and as a liquid fertilizer or used for its production. The method of claim 14, wherein the residual liquid cleaned by means of the reverse osmosis process and a thereby formed further residual liquid as liquid fertilizer or used for its production. The method of claim 15, wherein an approximately the volume of the withdrawn residual liquid and / or other residual liquid corresponding volume of liquid (F, P) added to the fermentation substrate is set. The method of claim 16, wherein as a liquid in the substrate (S1) or in the further substrate (S2) contained water is used. The method of claim 17, wherein remaining Difference volume by the addition of further liquid, preferably fresh water (F), residual water or wastewater, is compensated.